JP5137456B2 - Electric power steering control device - Google Patents

Description

  The present invention relates to an electric power steering control device used in an electric power steering system.

  In an electric power steering system, for example, during steering of an automobile, a steering assist force is applied by an electric motor so that a driver can perform the steering with a small force (for example, see Patent Documents 1 to 3 below). . In order to improve the steering feeling of the steering, in Patent Document 1, the assist current command value is determined by the output of the torque sensor that detects the steering torque of the steering and the output of the vehicle speed sensor that detects the vehicle speed of the vehicle. Obtained by multiplying the differential amount of the torque sensor output by the differential gain determined by the output of the torque sensor and the vehicle speed to determine the differential command value, and adding the assist current command value and the differential command value. The assist motor is driven by the command value.

  Also, in Patent Document 2, an assist torque value (motor current command value) is calculated based on the steering torque and the vehicle speed, and the viscosity for compensating the steering viscosity based on the steering angular speed (motor rotational speed) and the vehicle speed. A command value obtained by calculating a compensation value, correcting the viscosity compensation value so that the viscosity becomes large at high vehicle speed and small at low vehicle speed, and adding the corrected viscosity compensation value to the assist torque value Thus, the assist motor is driven.

  Further, in Patent Document 3, a steering assist command value is calculated based on the steering torque and the vehicle speed, a current control value is calculated from the steering assist command value and the motor current value, and the motor output current and the terminal voltage are calculated. The angular velocity of the motor (steering angular velocity) is estimated from the motor, the angular velocity is multiplied by a constant with a predetermined gain according to the angular velocity of the motor to obtain a convergence signal (convergence control value), and the steering of the steering is calculated from the angular velocity of the motor and the output current. The state is detected, and when the angular velocity of the motor is equal to or higher than the predetermined value and the output current is higher than the predetermined value, the gain is switched, and the motor is driven by the command value obtained by subtracting the convergence signal from the current control value. ing.

JP-A-10-291482 Japanese Patent No. 2782254 Japanese Patent No. 3637714

  As described in Patent Document 1 described above, only by changing the assist current command value and the differential command value according to the steering torque and the vehicle speed, the adjustment accuracy of the command value becomes rough, and the steering swing at the time of steering during traveling is increased. There is a risk that the steering feeling will deteriorate. Further, as in Patent Documents 2 and 3, the assist torque value or the current command value is changed according to the steering torque and the vehicle speed, and the viscosity compensation value or the convergence signal is changed according to the steering angular speed and the vehicle speed or the motor output current. However, the adjustment accuracy of the command value becomes rough, and the amount of change in the steering torque cannot be accommodated, and the steering feeling may be deteriorated.

  The present invention solves the above problems, and an object thereof is to provide an electric power steering control device capable of improving the steering feeling of the steering regardless of the state of steering and traveling. There is to do.

  An electric power steering control device according to the present invention includes a steering torque input means for inputting a steering torque of a steering wheel, a vehicle speed input means for inputting a vehicle speed of a vehicle, and a rotation of an electric motor for applying an assisting force to steering of the steering. Rotational speed input means for inputting speed, first current command value calculating means for calculating a first current command value based on steering torque and vehicle speed, and differential command value for differentiating steering torque to calculate a differential command value A second calculation unit, a second differential command value coefficient calculation unit that calculates a derivative command value coefficient based on the steering torque and the vehicle speed; A second current command value calculating means for calculating a current command value; a convergence command value calculating means for calculating a convergence command value based on the vehicle speed and the rotational speed; and subtracting the convergence command value from the second current command value. It includes a third current command value calculating means for calculating a third current command value, a current instruction value output means for outputting a third current command value to the motor driving means for driving the electric motor.

  According to this, the differential command value is calculated based on the steering torque, the coefficient of the first current command value and the differential command value is calculated based on the steering torque and the vehicle speed, and the differential command value, the coefficient, and the first current command value are calculated. A second current command value is calculated based on the vehicle speed and the rotation speed of the electric motor, and a third current command value is calculated based on the second current command value and the convergence command value. . For this reason, by calculating the control amount according to the control target, the adjustment accuracy of the third current command value becomes finer, and it corresponds to the amount of change in the steering torque and the swing of the steering during steering during traveling. Therefore, the steering feeling of the steering can be improved regardless of the state of steering and traveling.

  According to the present invention, in the electric power steering control device, the coefficient of the differential command value is large when the steering torque is neutral and the steering torque increases when the vehicle speed is 0 in a predetermined steering torque range. Get smaller. Alternatively, the coefficient of the differential command value is small when the steering torque is neutral and increases as the steering torque increases when the vehicle speed is zero within a predetermined steering torque range.

  According to this, the change state of the coefficient of the differential command value during the stop is set to any one of the above according to the change state (change tendency, level, etc.) of other parameters such as the first current command value and the convergence command value. By setting, the third current command value is changed so that the vibration due to the cogging torque at the time of the large steering angle when the steering torque is large during the stop and the swing of the steering due to the overshoot of the current at the neutral time when the steering torque is small ( It is possible to prevent a so-called “smooth feeling” and to improve the steering feeling of the steering.

  Further, according to the present invention, in the electric power steering control device described above, the coefficient of the differential command value is small and the steering torque is increased when the steering torque is neutral when the vehicle is running within a predetermined steering torque range. It grows as you go. Alternatively, the coefficient of the differential command value is large when the steering torque is neutral and decreases as the steering torque increases when the vehicle is traveling within a predetermined steering torque range.

  According to this, by setting the change state of the coefficient of the differential command value during traveling to one of the above according to the change state of other parameters such as the first current command value and the convergence command value, the first 3 By changing the current command value, it is possible to prevent the steering response from being insufficient due to the overshoot of the current when turning at the large steering angle position while traveling and the delay at the turning position at the neutral position. The feeling can be improved.

  According to the present invention, by calculating the control amount according to the control target, the adjustment accuracy of the third current command value becomes finer, the amount of change in the steering torque, and the steering swing during steering during traveling. Therefore, it is possible to improve the steering feeling of the steering regardless of the state of steering and traveling.

  FIG. 1 is a diagram showing an electric power steering system 100. The electric power steering system 100 is mounted on an automobile. When the steering 1 is rotated, the steering force is transmitted to the gear mechanism 3 via the shaft 2 a and further transmitted to the shaft 6 via the shaft 2 b and the gear mechanism 5. Then, the shaft 6 is driven to change the direction of the wheel 8 via the link mechanism 7. The electric motor 30 is driven to rotate in order to give an assisting force to the steering of the steering 1. When the motor 30 is rotationally driven, the driving force is transmitted to the gear mechanism 3 through the clutch 4 and further transmitted to the shaft 6 through the shaft 2 b and the gear mechanism 5. Then, driving of the shaft 6 and turning of the wheel 8 are assisted. That is, steering by the steering 1 is assisted by the motor 30. The torque sensor 11 detects a steering torque applied by the steering 1. The vehicle speed sensor 12 detects the vehicle speed (traveling speed) of the automobile. The ECU (electronic control unit) 10 detects the rotation speed of the motor 30. The ECU 10 also controls the clutch 4 to be ON (coupled) / OFF (disengaged). The ECU 10 further determines a current command value for driving the motor 30 based on the steering torque detected by the torque sensor 11, the vehicle speed detected by the vehicle speed sensor 12, and the rotational speed of the motor 30, and sets the current command value to the current command value. Based on this, the drive of the motor 30 is controlled. The ECU 10 constitutes an embodiment of an electric power steering control device according to the present invention. The battery 9 supplies electric power to the ECU 10 and the motor 30.

  FIG. 2 is a diagram illustrating functional blocks of the ECU 10. A portion surrounded by a one-dot chain line is a function executed by a program in the ECU 10. The steering torque T of the steering 1 detected by the torque sensor 11 is input to the differentiator 13, the differential gain table 14, and the assist current table 15. The vehicle speed V of the automobile detected by the vehicle speed sensor 12 is input to the differential gain table 14, the assist current table 15, and the gain changer 22. The motor inter-terminal voltage detection unit 18 detects the inter-terminal voltage E of the motor 30 and outputs it to the motor rotation speed estimation unit 20. The motor current detection unit 19 detects the current C flowing through the motor 30 and outputs it to the motor rotation speed estimation unit 20. The motor rotation speed estimation unit 20 detects the rotation speed (steering speed) R of the motor 30 based on the voltage E between the terminals of the motor 30 and the current C, and outputs it to the convergence command value table 21.

The differentiator 13 calculates a differentiation command value T ₁ by differentiating the steering torque T with respect to time, and outputs it to the multiplier 16. The differential gain table 14 calculates a differential gain (coefficient of the differential command value T ₁ ) G ₁ based on the steering torque T and the vehicle speed V, and outputs it to the multiplier 16. Specifically, the differential gain table 14 stores in advance two types of differential gain curves that vary depending on the vehicle speed V as shown in FIG. If the vehicle speed V is 0 (V = 0, stop) the differential gain curve of the differential gain G _1, in the range of the predetermined steering torque T (0 to ± Ta), when neutral steering torque T (T = 0) and decreases as the absolute value of the steering torque T increases, and becomes constant when the absolute value of the steering torque T exceeds a certain value ± Ta. If the vehicle speed V is not 0 (V >> 0, during running) by the differential gain curve of the differential gain _{G 1,} in the range of the predetermined steering torque T (0 to ± Ta), at the neutral position (T of the steering torque T = 0) and increases as the absolute value of the steering torque T increases, and becomes constant when the absolute value of the steering torque T exceeds a certain ± value Ta. Further, when the vehicle speed V is 0 (V = 0, stop) differential gain _{G 1} of the case where the vehicle speed V is not 0 (V >> 0, the running time) always greater than the differential gain _{G 1} of the. Differential gain table 14 selects one of the differential gain curves according to the vehicle speed V, the calculating the differential gain G ₁ and a fine fraction gain curve and the steering torque T.

The assist current table 15 (FIG. 2) calculates an assist current (first current command value) I ₁ based on the steering torque T and the vehicle speed V, and outputs it to the adder 17. Specifically, in the assist current table 15, two types of assist current curves different depending on the vehicle speed V are stored in advance as shown in FIG. The assist current I ₁ indicated by each assist current curve coincides in the vicinity of the neutral position of the steering torque T in the predetermined steering torque T range (0 to ± Tb), and the steering torque T increases to the positive (+) side. Increases as the steering torque T increases toward the negative (−) side, and decreases when the absolute value of the steering torque T exceeds a certain value ± Tb. Further, the assist current I ₁ when the vehicle speed V is 0 (V = 0, when stopped) is greater than the assist current I ₁ when the vehicle speed V is not 0 (V >> 0, when traveling). The amount of increase / decrease with increasing absolute value is large. The assist current table 15 selects any assist current curve according to the vehicle speed V, and calculates the assist current I ₁ from the assist current curve and the steering torque T.

The multiplier 16 (FIG. 2) multiplies the differential command value T ₁ and the differential gain G ₁ and outputs the result to the adder 17. The adder 17 calculates a second current command value I ₂ by adding the product of the differential command value T ₁ and the differential gain G ₁ and the assist current I _1, and outputs the second current command value I ₂ to the subtractor 24. The convergence command value table 21 calculates a first convergence command value D ₁ based on the rotational speed R of the motor 30 and outputs the first convergence command value D ₁ to the multiplier 23. Specifically, a convergence command value curve as shown in FIG. 6 is stored in advance in the convergence command value table 21. First converging command value D ₁ shown astringent command value curve becomes larger with the rotation speed R of the motor 30 increases, and becomes constant exceeds a certain rotational speed R value Ra. The convergence command value table 21 calculates a first convergence command value D ₁ from the convergence command value curve and the rotation speed R.

Gain modifier 22 (FIG. 2) changes the convergence gain G ₂ based on the vehicle speed V, the output to the multiplier 23. Specifically, the gain changer 22 stores in advance a convergence gain curve as shown in FIG. Converging gain G ₂ indicated by the convergence gain curve is large when the vehicle speed V is zero, and increases after becoming once reduced As the vehicle speed V increases, and becomes constant exceeds a value Vc which is the vehicle speed V . Moreover, converging the gain _{G 2} is, the vehicle speed V becomes the minimum value when the low-speed Va~Vb (20~30km / h). Gain modifier 22 calculates the convergence gain G ₂ and a convergence gain curve and the vehicle speed V. The multiplier 23 (FIG. 2) calculates the second convergence command value D ₂ by multiplying the first convergence command value D ₁ and the convergence gain G ₂ and outputs the second convergence command value D ₂ to the subtracter 24. Subtractor 24, by the second current command value I ₂ subtracts the second converging command value D ₂ calculates the third current command value I _3, and outputs to the motor drive unit 25 shown in FIG.

FIG. 3 is a diagram illustrating a motor driving unit 25 for driving the motor 30. The motor drive unit 25 is provided in the ECU 10. The motor drive unit 25 drives the motor 30 in PWM (pulse width modulation) control based on the third current command value I ₃ which is input from the subtracter 24 of FIG. Specifically, the motor drive unit 25 includes an FET gate drive circuit 26, a boost power supply 27, an H bridge circuit including FETs 31 to 34, and the like. The FET gate drive circuit 26 drives the gates of the FETs 31 to 34 based on the third current command value I ₃ . The step-up power supply 27 drives the high side of the FETs 31 and 32. When the motor 31 is driven, the FET 31 or the FET 32 is switched ON / OFF by a PWM signal having a predetermined duty ratio determined based on the third current command value I ₃ . The FET 33 or the FET 34 is turned on when the motor 30 is driven. The FETs 31 to 34 to be driven are switched according to the rotation direction of the motor 30 determined from the sign of the PWM signal.

For example, by controlling ON / OFF of the FET 31 when the FET 34 is in the ON state, a current having a level corresponding to the third current command value I ₃ is supplied from the power supply 28 through the FET 31, the motor 30, the FET 34, and the resistor 36. The motor 30 is driven to rotate in the forward direction. In addition, when the FET 33 is in the ON state, the FET 32 is controlled to be turned on / off, so that a current of a level corresponding to the third current command value I ₃ passes from the power source 28 through the FET 32, the motor 30, the FET 33, and the resistor 35. The motor 30 is driven to rotate in the reverse direction.

According to the above, calculates the differential command value T ₁ based on the steering torque T of the steering wheel 1, a first current command value I ₁ based on the steering torque T and the vehicle speed V to calculate the derivative gain G _1, the differential command value The second current command value I ₂ is calculated based on T ₁ , the differential gain G ₁ and the first current command value I ₁ , the first convergence command value D ₁ is calculated based on the rotational speed R of the motor 30, and the vehicle speed second calculating a convergence command value D ₂ on the basis of V a first convergent command value D _1, calculates a second current command value I ₂ and the third current command value I ₃ on the basis of the second converging command value D ₂ doing. Therefore, by calculating the third current command value I ₃ for driving the motor 30 according to the control target, the adjustment accuracy of the third current command value I ₃ becomes finer, and the amount of change in the steering torque T can be reduced. It is possible to deal with the size and the swing of the steering wheel 1 during steering during traveling, and the steering feeling of the steering wheel 1 can be improved regardless of the state of steering and traveling.

Further, the vehicle speed V is zero when (vehicle at rest), the differential gain G ₁ of that large and the steering torque T to the neutral state of the steering torque T is smaller As the increase, the third current command value by changing the I _3, the vibration caused by cogging torque when a large steering angle steering torque T is large in the stop, the steering torque T is small (0) whirling of the steering wheel 1 by an overshoot of the neutral at the current ( It is possible to prevent a so-called “pull feeling” and to improve the steering feeling of the steering 1.

Further, when the vehicle speed V is not zero (car is traveling), the differential gain G ₁ by small and the steering torque T to the neutral state of the steering torque T is larger him to increase, the third current command value I ₃ can be prevented to prevent the steering 1 from being insufficiently touched due to an overshoot of the current when turning at a large rudder angle position while traveling, and a delay at the time of turning back at the neutral position. It becomes possible to make a ring favorable.

Further, by increasing brought first convergence command value D ₁ to the rotational speed R of the motor 30 increases, as the rotational speed R, i.e. the steering angular velocity is increased, and brakes the motor 30, the current It is possible to improve the steering feeling of the swinging 1 so as to suppress the overshoot of the steering 1 and to prevent the steering 1 from swinging during steering during high speed traveling.

Further, the converging gain G ₂ As the large and the vehicle speed V when the vehicle speed V 0 increases by increasing from when the once reduced, the second converging command value D ₂ also the vehicle speed V is large when the 0 And as the vehicle speed V increases, it decreases and then increases. Therefore, it is possible at the time of stopping, by the second converging command value D ₂ is larger, the third current command value I ₃ is changed to prevent the whirling steering 1 according to current overshoot. At the same time, it is possible to prevent a sudden increase in the steering torque T accompanying an increase in the steering speed (the rotational speed R of the motor 30). That is, when the vehicle speed is the second converging command value D ₂ is smaller at 0, exceeds the value Rb where there is steering speed R as shown by the one-dot chain line in FIG. 8, while the steering torque T increases sharply , when the vehicle speed second converging command value D ₂ is greater when 0, with increasing steering speed R as shown by the solid line in FIG. 8, the steering torque T is gradually increased, the operation load of the steering wheel 1 is It is reduced.

Further, at the time of low speed running, by the second converging command value D ₂ is smaller, the third current command value I ₃ is changed, it is possible to easily return the steering wheel 1 from the large steering angle position to the neutral position. Furthermore, during high-speed traveling, by the second converging command value D ₂ is larger, the third current command value I ₃ is changed, it is possible to prevent the whirling steering 1 during steering.

In the above mentioned embodiment, the differential gain G ₁ as shown in FIG. 4, when the vehicle speed V is zero, and smaller As the large and the steering torque T to the neutral state of the steering torque T increases, vehicle speed Although an example in which the steering torque T is small when the steering torque T is neutral and increased as the steering torque T increases when V is not 0 has been described, the present invention is not limited to this. Other than this, depending on other parameters change state such as the first current command value I ₁ and the first convergence command value D ₁ and converging gain G ₂ (change trends and level, etc.), for example, in FIG. 9 the differential gain _{G 1} as shown in a range of a predetermined steering torque T (0~ ± Ta), when the vehicle speed V is 0 (V = 0), when neutral steering torque T (T = 0) It may be small and increase as the steering torque T increases. Further, the differential gain G _1, in the range (0 to ± Ta) of predetermined steering torque T, when the vehicle speed V is not 0 (V >> 0), is large and the steering torque T when the neutral steering torque T increases You may make it small as it does. In other words, the change state of the differential gain G ₁ may be set in accordance with the changing state of the other parameters. In this way, vibration due to cogging torque at the time of the large rudder angle during stoppage, swing of the steering wheel 1 due to overshoot of the current at neutrality during stoppage, and overcurrent at the time of turning back at the large rudder angle position during traveling Insufficient response of the steering wheel 1 due to the chute and a delay when turning back at the neutral position during traveling can be prevented, and the steering feeling of the steering wheel 1 can be improved.

In the embodiment described above, as shown in FIGS. 4, 5, and 9, when the vehicle speed V is not 0 (V >> 0, during traveling), one type of differential gain curve and assist current are used. It gave the example of differential gain G ₁ and the assist current I ₁ was changed respectively according to curve, but the present invention is not limited only thereto. In addition to this, for example, as shown in FIGS. 10 to 12, when the vehicle speed V is not 0, the differential gain G ₁ and the assist according to a plurality of types of differential gain curves and assist current curves according to the range of the magnitude of the vehicle speed V. the current I ₁ may be varied, respectively. 10 to 12, for example, Vx = 5 km / h, Vy = 20 km / h, and Vz = 40 km / h are set.

It is a figure showing an electric power steering system. It is a figure which shows the functional block of ECU. It is a figure which shows a motor drive part. It is a figure which shows a differential gain curve. It is a figure which shows an assist current curve. It is a figure which shows a convergence command value curve. It is a figure which shows a convergence gain curve. It is a figure which shows the change of steering speed and steering torque. It is a figure which shows other embodiment. It is a figure which shows other embodiment. It is a figure which shows other embodiment. It is a figure which shows other embodiment.

Explanation of symbols

1 Steering 10 ECU
DESCRIPTION OF SYMBOLS 11 Torque sensor 12 Vehicle speed sensor 13 Differentiator 14 Differential gain table 15 Assist current table 16, 23 Multiplier 17 Adder 20 Motor rotational speed estimation part 21 Convergence command value table 22 Gain changer 24 Subtractor 25 Motor drive part 30 Electric motor

Claims (4)

Steering torque input means for inputting the steering torque of the steering;
Vehicle speed input means for inputting the vehicle speed;
A rotational speed input means for inputting a rotational speed of an electric motor for applying auxiliary force to steering of the steering;
First current command value calculating means for calculating a first current command value based on the steering torque and the vehicle speed;
Differential command value calculating means for differentiating the steering torque to calculate a differential command value;
Differential command value coefficient calculating means for calculating a coefficient of the differential command value based on the steering torque and the vehicle speed;
Second current command value calculating means for calculating a second current command value by multiplying the differential command value and the coefficient and adding the first current command value;
A convergence command value calculating means for calculating a convergence command value based on the vehicle speed and the rotational speed;
A third current command value calculating means for calculating a third current command value by subtracting the convergence command value from the second current command value;
Current command value output means for outputting the third current command value to motor drive means for driving the electric motor,
The coefficient of the differential command value is large when the steering torque is neutral in the predetermined range of the steering torque and becomes smaller as the steering torque increases when the vehicle speed is zero. Electric power steering control device. Steering torque input means for inputting the steering torque of the steering;
Vehicle speed input means for inputting the vehicle speed;
A rotational speed input means for inputting a rotational speed of an electric motor for applying auxiliary force to steering of the steering;
First current command value calculating means for calculating a first current command value based on the steering torque and the vehicle speed;
Differential command value calculating means for differentiating the steering torque to calculate a differential command value;
Differential command value coefficient calculating means for calculating a coefficient of the differential command value based on the steering torque and the vehicle speed;
Second current command value calculating means for calculating a second current command value by multiplying the differential command value and the coefficient and adding the first current command value;
A convergence command value calculating means for calculating a convergence command value based on the vehicle speed and the rotational speed;
A third current command value calculating means for calculating a third current command value by subtracting the convergence command value from the second current command value;
Current command value output means for outputting the third current command value to motor drive means for driving the electric motor,
The coefficient of the derivative command value is small when the steering torque is neutral and increases as the steering torque increases when the vehicle speed is zero within a predetermined range of the steering torque. Electric power steering control device. Steering torque input means for inputting the steering torque of the steering;
Vehicle speed input means for inputting the vehicle speed;
A rotational speed input means for inputting a rotational speed of an electric motor for applying auxiliary force to steering of the steering;
First current command value calculating means for calculating a first current command value based on the steering torque and the vehicle speed;
Differential command value calculating means for differentiating the steering torque to calculate a differential command value;
Differential command value coefficient calculating means for calculating a coefficient of the differential command value based on the steering torque and the vehicle speed;
Second current command value calculating means for calculating a second current command value by multiplying the differential command value and the coefficient and adding the first current command value;
A convergence command value calculating means for calculating a convergence command value based on the vehicle speed and the rotational speed;
A third current command value calculating means for calculating a third current command value by subtracting the convergence command value from the second current command value;
Current command value output means for outputting the third current command value to motor drive means for driving the electric motor,
The coefficient of the differential command value is small when the steering torque is neutral and increases as the steering torque increases when the vehicle is running within a predetermined range of the steering torque. Electric power steering control device. Steering torque input means for inputting the steering torque of the steering;
Vehicle speed input means for inputting the vehicle speed;
A rotational speed input means for inputting a rotational speed of an electric motor for applying auxiliary force to steering of the steering;
First current command value calculating means for calculating a first current command value based on the steering torque and the vehicle speed;
Differential command value calculating means for differentiating the steering torque to calculate a differential command value;
Differential command value coefficient calculating means for calculating a coefficient of the differential command value based on the steering torque and the vehicle speed;
Second current command value calculating means for calculating a second current command value by multiplying the differential command value and the coefficient and adding the first current command value;
A convergence command value calculating means for calculating a convergence command value based on the vehicle speed and the rotational speed;
A third current command value calculating means for calculating a third current command value by subtracting the convergence command value from the second current command value;
Current command value output means for outputting the third current command value to motor drive means for driving the electric motor,
The coefficient of the differential command value is large when the vehicle is running within a predetermined range of the steering torque, and becomes small as the steering torque increases when the steering torque is neutral. Electric power steering control device.

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